Dual filament readout lamp

ABSTRACT

A readout lamp for producing numeric or alpha-numeric displays in which two sets of incandescent filament segments in parallel spaced relationship with each other are employed to produce a double lined number or letter. Failure of one or more filaments will still enable the lamp to produce an intelligible display. The two sets of filaments are slightly displaced vertically from each other to prevent electrical contact without destroying the substantially uniplanar appearance of the display.

O United States Patent 1 1 1111 3,743,880

Demarest July 3, 1973 [54] DUAL FILAMENT READOUT LAMP 2,862,147 11/1958Conti 313/316 X 2,878,418 3/1959 Garfinkel et a1 315/69 [751 Invent:Philip nemres" Pme 3,408,523 10/1968 Demarest et a1 313/316 x 73Assigneez Ref Technohgy Devehpmem 3,418,509 12/1968 Frouws et al.3111/1095 Corporation, New York, N.Y. Primary Examiner-Robert Segal [22]filed: May 1971 Attorney-Lawrence l. Lerner, Sidney David, Joseph S.[21] Appl. No,; 141,009 Littenberg and Richard 1. Samuel Related US.Application Data [63] Continuation of Ser. No. 806,431, March l2 1969,[57] ABSTRA CT abandoned A readout lamp for produemg numeric oralphanumeric displays in which two sets of incandescent fila- 52 us.(:1. 3113/1095, 313/316 mam Segments in Parallel spaced relationshipwith each 51 Int. Cl. H0lk 9/00, H01 j 61/66 other are employed toProduce a double lined number 5 Field f Search u 3 5 9; 3 3 R, orletter. Failure of one or more filaments will still en- 313/108 H, 1095,2 0 316 able the lamp to produce an intelligible display. The two setsof filaments are slightly displaced vertically [56] References Citedfrom each other to prevent electrical contact without UNITED STATESPATENTS destroying the substantially uniplanar appearance of thedisplay. 1,787,470 1/1931 Bone 313/316 X 2,391,922 1/1946 1 Claim, 7Drawing Figures Roper 313/316 X Patented July 3, 1973 I 3,743,880

FIG. 3 mlqllimllfl li H DUAL FILAMENT READOUT LAMP This application is acontinuation of application Ser. No. 806,431, filed Mar. 12, 1969, nowabandoned.

BACKGROUND OF THE INVENTION Incandescent filament lamps have been usedin alpha-numeric displays but they have been limited in their usefulnessfor several reasons: A filament burn out can go un-noticed for some timeand give a faulty reading, the arrangement of filament supporting posts,if carried through the envelope base, produces a complex pattern whichis difficult to base; where the lamps are miniaturized the light outputmay be insufficient. The present invention provides two parallel directviewing filament systems for each portion of the display. If onefilament or a segment of one filament burns out, the other filamentcontinues to function and gives notice that the lamp should be replaced.By using a printed circuit between an inner ceramic slab and a ceramicbase there is no chance of short circuit between wires, the lead-in pinscan be grouped in an orderly array, and considerable space is saved.

A feature of the present invention is a novel grouping of lampcomponents to reduce the size of readout lamps.

Another feature of the invention is the manner in which the filamentposts are secured to a ceramic slab and connected to leadin conductors.

A further function is the increased reliability secured through the useof dual filament systems.

BRIEF DESCRIPTION OF THE FIGURES For a better understanding of thepresent invention, together with other details and features thereof,reference is made to the following description taken in connection withthe accompanying drawings.

FIG. 1 is a plan view of the readout lamp showing the position of thefilaments.

FIG. 2 is a view of the base side of the lamp showing the 15 lead-inpins.

FIG. 3 is a side view of the lamp.

FIG. 4 is an isometric view of the ceramic slab showing the filamentsand their supporting posts, somewhat enlarged.

FIG. 5 is a cross sectional view of the lamp taken along line 5-5 ofFIG. 2 on an enlarged scale.

FIG. 5a is a view similar to FIG. 5 showing an alternate form.

FIG. 6. is a'plan view of the bottom side of the ceramic slab showingthe printed circuit connections.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1, 2, and3, the readout lamp includes an envelope which is made up of a toptransparent glass layer ll, a support ring 12 of metal, and a ceramicbase I3. Inside the envelope 10 there are a plurality of filaments 14having their ends secured to posts 15. The filiments 14 are formed oftungsten wire and the posts 15 are preferably made of Kovar since theyare set into and secured to a ceramic slab 16. The slab 16 is first madewith all the holes and depressions needed and is then metalized byadding an alloy of molybdenum-manganese to all surfaces except the topand bottom. The printed circuits are now added to the bottom surface ofthe slab by any of the well known methods.

FIG. 6 shows the general layout of the connections. A ground cavity 17is connected by a conductive film 18 to 10 of the holes which are toreceive the posts 15. The ground cavity 17 is to act as the commonconnection for all the filaments l4. Conductive films 20 are alsodeposited between selected depressions 21 and other post holes.

The slab 16 is now ready for the tungsten filaments 14. These are strungbetween the top ends of the posts 15 and secured by welding or any othersuitable mans. The arrangement of filaments is shown in FIGS. 1 and 4.

The base 13 is next fabricated in a manner similar to the preparation ofthe slab 16. After the holes 22 for the lead-in pins 23 have beenproperly formed, the base 13 is metalized on all surfaces except the topand bottom. Then the entire lamp can be assembled, inserting all thepins 23 in their holes 22, applying the Kovar ring 12 onto the step 13aat the periphery of the base 13, dropping the slab 16 into the recess,and finally placing the glass top 1 l on the Kover ring. The assembledlamp is now placed in a hydrogen furnace and the metalized surfaces arefused to each other. Contacts are thereby made between the lead-in pins23 and the printed circuit films. The posts 15 are joined to the circuitfilms and mechanically secured as well. The lamp is now ready forpumping and filling with an inert gas such as argon. Evacuation may bedone through a hollow pin 23 which is finally pinched off.

When the lamp is in use, the filaments are not heated to fullbrilliance, i.e. the brightners associated with incandescent lamps. Theoberver looks directly at the lamp and observes the display. For someinstallations little more than red heat is necessary. Under theseconditions of use, the filaments have a life of over 100,000 hours.

An examination of the preferred embodiment illustrated in the drawingwill show that the display character is formed by a seven segmentarrangement of incandescent tungsten filaments or light bars 14. Spacedinwardly from the first set of light bars is a second seven segment setof filaments, paralled to but slightly vertically displaced along the Zaxis from the first set. The two sets of filaments may be electricallyand mechanically separate to provide substantially parallel arrangedcharacters. The adjacent filaments are preferably sufficiently separatedto indicate mode failure.

With suitable switching means well known in the art, it is possible toselect specific filainents in either of these displays to form lettersor numerals if so desired or employ both displays at the same time.Where both displays are employed at once, additional illumination isavailable for ease in reading.

It will be apparent that failure of one or more of the filaments in thedual filament readout lamp will still provide an intelligible image totheobserver. This dual reliability or redundancy may be of extremeimportance where the lamp is used in cockpit displays, multiplexsystems, and the like.

FIG. 5a illustrates an alternate form of the present invention is whichdielectric block, 24 is placed within the envelope 10. The block 24 issuitably channeled to receive the filaments l4 and posts 15 therein. Inthe event of a burn-out or a break in any of the filament segments thedielectric block 24 will prevent contact and possible damage by thebroken portion to the adjacent filaments.

Having thus fully described the invention, what is l. A miniature dualfilament system numeric or alpha-numeric readout lamp comprising:

a sealed envelope;

a transparent faceplate for said envelope;

a ceramic slab spaced from and beneath said transparent faceplate;

a ring sealingly connecting the peripheries of said faceplate and slab;

a first plurality of electrically conductive posts secured at one end tosaid slab and extending above its upper surface towards said transparentfaceplate; said first plurality of electrically conductive posts beingarranged in a first predetermined pattern;

a first set of incandescent filaments secured to the free ends of saidfirst plurality of electrically conductive posts for the passage ofcurrent and for selectively producing a first display;

a second plurality of electrically conductive posts secured at one endto said slab and extending above its upper surface towards thetransparent faceplate arranged in a second predetermined pattern similarto said first predetermined pattern;

each of said second plurality of electrically conductive posts beingadjacent to one of said first plurality of electrically conductiveposts;

a second set of incandescent filaments vertically displaced from saidfirst set of filaments a distance sufficient to permit filamentcross-over while retaining the substantially uniplanar aspect of thedisplay and secured to the free ends of said second plurality ofelectrically conductive posts for the passage of current and forselectively producing a second display;

said second set of filaments being disposed substantially parallel tosaid first set of filaments so that said second display is substantiallythe same as said first display;

electrically connecting means on the surface of said slab opposite saidfilaments in contact with said posts, said means including separateconnections for each free end so that the display produced by the firstset of incandescent filaments is independent of the display produced bythe second set of incandescent filaments;

a plurality of lead-in conductors for said connecting means forconnecting the filaments to'an external source of power; and

a block of dielectric material having filament receiving bores therein,and means to support the block within the sealed envelope.

1. A miniature dual filament system numeric or alpha-numeric readoutlamp comprising: a sealed envelope; a transparent faceplate for saidenvelope; a ceramic slab spaced from and beneath said transparentfaceplate; a ring sealingly connecting the peripheries of said faceplateand slab; a first plurality of electrically conductive posts secured atone end to said slab and extending above its upper surface towards saidtransparent faceplate; said first plurality of electrically conductiveposts being arranged in a first predetermined pattern; a first set ofincandescent filaments secured to the free ends of said first pluralityof electrically conductive posts for the passage of current and forselectively producing a first display; a second plurality ofelectrically conductive posts secured at one end to said slab andextending above its upper surface towards the transparent faceplatearranged in a second predetermined pattern similar to said firstpredetermined pattern; each of said second plurality of electricallyconductive posts being adjacent to one of said first plurality ofelectrically conductive posts; a second set of incandescent filamentsvertically displaced from said first set of filaments a distancesufficient to permit filament cross-over while retaining thesubstantially uniplanar aspect of the display and secured to the freeends of said second plurality of electrically conductive posts for thepassage of current and for selectively producing a second display; saidsecond set of filaments being disposed substantially parallel to saidfirst set of filaments so that said second display is substantially thesame as said first display; electrically connecting means on the surfaceof said slab opposite said filaments in contact with said posts, saidmeans including separate connections for each free end so that thedisplay produced by the first set of incandescent filaments isindependent of the display produced by the second set of incandescentfilaments; a plurality of lead-in conductors for said connecting meansfor connecting the filaments to an external source of power; and a blockof dielectric material having filament receiving bores therein, andmeans to support the block within the sealed envelope.